Thermal hysteresis in the luminescence ofYb3+ions inSr0.6Ba0.4Nb2O6

The optical spectra of ${\mathrm{Yb}}^{3+}$ ions in congruent, ${\mathrm{Sr}}_{0.6}{\mathrm{Ba}}_{0.4}{\mathrm{Nb}}_{2}{\mathrm{O}}_{6}$ (SBN) crystals have been systematically investigated in a broad temperature range $(10\char21{}420\phantom{\rule{0.3em}{0ex}}\mathrm{K})$. Laser site selective low temperature fluorescence spectra have shown that ${\mathrm{Yb}}^{3+}$ ions enter in four different cationic lattice sites. A thermal hysteresis in both bandwidth and luminescence intensity of ${\mathrm{Yb}}^{3+}$ ions has been detected in the temperature range $(300\char21{}400\phantom{\rule{0.3em}{0ex}}\mathrm{K})$ around the ferro to paraelectric phase transition. This behavior has been explained as a result of the local structural modifications that take place around the ${\mathrm{Yb}}^{3+}$ ions when the crystal becomes nonpolar, which affect in a different way the luminescence of ${\mathrm{Yb}}^{3+}$ ions located in the different sites. Off-congruent SBN crystals activated with ${\mathrm{Yb}}^{3+}$ ions have been grown and investigated in order to examine the possibilities of extending the detected hysteretic behavior to other temperature ranges.